Spacecraft include a plethora of equipment, such as electronic equipment, that generates heat. This heat must be dissipated, and because space is essentially void of air, the heat must be radiated to outer space. Spacecraft, such as satellites, typically include radiator panels that draw the heat from electronics and other equipment to an outer surface of the spacecraft.
With reference to the schematic diagram of FIG. 1, a typical prior art radiator panel 10 includes an inside face-sheet 12 that faces the inside of the spacecraft, an outside face-sheet 14 that faces the outside of the spacecraft toward outer space, a honeycomb core 16 positioned between the face-sheets to give the panel structural support, and one or more heat pipes 18 positioned between the face-sheets to translate the heat generated by an electronics package 20 away from the electronics package 20 to the outside face-sheet 14 and ultimately to outer space. Heat pipes are heat transfer devices that rely on phase transition of a working fluid to transfer heat from one location to another, such as from an electronic device to a heat sink, or in the application of a spacecraft, ultimately to outer space.
As seen in FIG. 1, the heat pipe 18 of the illustrated prior art radiator panel 10 includes a flange 22 extending from a body 24, with the flange 22 partially penetrating, or extending through, the inside face-sheet 12. The electronics package 20 is mounted to the flange 22 with a gasket 26 positioned between the electronics package 20 and the flange 22, and heat from the electronics package 20 conducts through the flange 22 to the body 24 of the heat pipe 18, for subsequent dissipation to outer space as discussed above. Because the flange 22 of the heat pipe 18 partially penetrates the inside face-sheet 12, the inside face-sheet 12 is required to be modified during assembly of the prior art radiator panel 10. That is, the inside face-sheet 12 is required to be machined, or otherwise modified, to include an opening 28 for the flange 22 to partially extend through. Moreover, because the body 24 of a flanged heat pipe 18 typically is extruded, the flange 22 initially extends the entire length of the heat pipe 18. Accordingly, during assembly of a typical prior art radiator panel 10, the flange 22 must be modified to only extend for a distance corresponding to a dimension of a package 20. Also, the honeycomb 16 is required to be modified to extend around the heat pipe 18, including the flange 22 of the heat pipe 18. This process during assembly of a radiator panel 10 may be referred to or described as core-stepping. During assembly of a prior art radiator panel 10, bolts 29 are utilized to secure the electronics package 20 to the heat pipe's flange 22.
As schematically illustrated in dashed lines in FIG. 1, prior art radiator panels 10 may include one or more stiffening members 19, such as in the form of an I-beam, on the internal surface of the inside face-sheet 12 to give the radiator panel 10 a desired stiffness. However, placement of stiffening members 19 presents several challenges with the design of prior art radiator panels 10 because of the various packages 20 and associated electronics, wiring harnesses, and other internal components of a spacecraft.
FIG. 2 schematically illustrates another typical prior art radiator panel 11. Prior art radiator panel 11 also includes an inside face-sheet 12, an outside face-sheet 14, a honeycomb core 16, and one or more heat pipes 18 for drawing heat away from an electronics package 20. The heat pipe 18 of prior art radiator panel 11, however, does not include a flange 22 that penetrates the inside face-sheet 12. Rather, prior art radiator panels 11 include epoxy-potted fasteners 13 that are positioned within bores 15 that are required to be machined through the inside face-sheet 12 and into the honeycomb core 16. Fasteners 13 receive bolts 29, and typically a layer of room-temperature vulcanizing (RTV) silicone sealer 17 is utilized between the electronics package 20 and the inside face-sheet 12. Fasteners 13 are not in mechanical communication with and do not engage the heat pipe 18. The joints formed by fasteners 13 and bolts 29 are subject to relaxation over time, and thus to mechanical creep, which results in an inefficient transfer of heat from the electronics package 20 to the heat pipe 18, and thus in an inefficient transfer of heat from the electronics package 20 to outer space.
Prior art radiator panels often include heat pipes that are over-sized, or that have the capability of transferring more heat than is required for the prior art radiator panel, because a desired stiffness of the radiator panel needs to be achieved. In other words, radiator panels of spacecraft are required to have an optimized stiffness in view of the conditions in which the spacecraft is launched, and the size of heat pipes are selected to achieve the optimized stiffness.